The present disclosure relates generally to automotive heat exchangers and, more particularly, to brazed heat exchangers.
Various types of heat exchangers are used in automotive applications. For example, WO 03093751, published on Nov. 13, 2003, assigned to Behr, relates to a radiator with an internal fin section, and a short section of tube inside a primary tube. In various evaporator applications, such as, for example, in WO 2004/005831, evaporators are provided with a fin that fits against the tube radius for the full length of the tube. U.S. Pat. No. 5,105,540 issued on Apr. 21, 1992 to Ford Motor Company shows a tube with an internal liner stock for increasing interior fluid turbulation. U.S. Pat. No. 4,501,321 issued on Feb. 26, 1985 to Blackstone Corporation shows a two piece tube with an overlap occurring at the minor dimension. U.S. Pat. No. 4,813,112, issued on Mar. 21, 1989 to Societe Anonyme des Usines Chausson shows a reinforcement plate on an ambient side of a header to locally reinforce a tube-to-header joint. U.S. Pat. No. 4,805,693 issued on Feb. 21, 1989 to Modine Manufacturing shows a two-piece tube with an overlap occurring at the diameter of the tube. The above references are herein incorporated by reference.
In recent years, the temperatures and pressures of so-called ‘turbo-charged’ air has significantly increased resulting in failure of heat exchangers, such as those of prior art charge air coolers (CACs), and after coolers due to thermal stresses. In such temperature/pressure conditions, a major disadvantage of prior art designs includes common failures, such as fatigue fracture, of both the tube and the internal fin.
In prior art designs, specific fractures, such as transverse fractures, may occur, for example, at tube locations, and, in particular, at the inlet header of the heat exchanger. Also, internal fin fracture may occur and lead to contamination in heat exchangers such as the charge air in coolers.
Higher temperatures and pressures for CACs are being specified by customers. Even with material changes, increased thickness of materials will be needed to meet these new requirements. Increasing material thickness further drives up costs. One solution is to increase the robustness of the tube by increasing the thickness of the tube and the internal fin. Another solution is to use high strength alloys. Although effective in improving durability, these changes require significant tooling, process change(s), material cost(s), and overall cost(s) to produce a durable charge air cooler.
There exists a need for a heat exchanger assembly with localized strength which is cost effective and improves durability with increasing pressure/temperature applications.